The perfect burger

1 lb good-quality bacon

1 small onion, chopped

4-5 garlic cloves, chopped

1/2 cup packed brown sugar

1/2 cup coffee

1/4 cup maple syrup

1 Tbsp. balsamic vinegar

1 Tbsp. grainy mustard

Roughly chop the bacon and cook it in a heavy pot; transfer to a bowl using a slotted spoon, draining off most of the drippings. Saute the onion and garlic cloves in the rest for 5 minutes, until soft and starting to turn golden. Return the bacon to the pan, add the brown sugar, coffee, maple syrup, vinegar and mustard and cook over medium heat for half an hour, or until deep golden and thickened to the consistency of jam. If you like, cool and pulse in the food processor for a finer texture. Serve warm or cold.